Shared channel structure, ARQ systems and methods

ABSTRACT

A forward link design is provided employing CDMA (code division multiple access) technologies in which time division multiplexing is employed between data and control information on the forward link to service multiple users per slot. Another forward link design employing CDMA (code division multiple access) technologies is provided in which code division multiplexing between data and control information is employed on the forward link to service multiple users per slot, which is preferably backwards compatible with legacy standards such as IS2000A. A reverse link design is also provided.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/983,365 filed Oct. 24, 2001.

This application claims the benefit of provisional application60/243,013 filed Oct. 24, 2000, provisional application 60/246,889 filedNov. 8, 2000, 60/250,734 filed Dec. 1, 2000, provisional application60/266,602 filed Feb. 5, 2001, and provisional application 60/277,951filed Mar. 23, 2001.

FIELD OF THE INVENTION

This invention relates to CDMA systems which provide both data and voicefunctionality.

BACKGROUND OF THE INVENTION

Code Division Multiple Access (CDMA) is a cellular technology originallystandardized as IS-95, which competes with GSM technology for dominancein the cellular world. CDMA employs spread-spectrum technology whichincreases the capacity of cellular systems. CDMA was adopted by theTelecommunications Industry Association (TIA) in 1993. Differentvariations now exist, with the original CDMA now known as cdmaOne. Forexample, there is now cdma2000 1×RTT and its variants like 1×EV-DO and1×EV-DV and 3×RTT Multi-Carrier (MC 3×). These basically refer tovariants of usage of a 1.25 MHz carrier channel. For example, MC 3×usesa 3.75 MHz carrier channel. By May 2001, there were 35 millionsubscribers on cdmaone systems worldwide.

Third Generation efforts under ITU's IMT-2000 initiative have beenmotivated in large part by a need to increase the supported data ratesover wireless channels. The demand for high rates has not been met bysecond generation systems since these systems have been defined anddesigned for only voice and low-rate data. Higher data rates requiremore bandwidth on the radio channel for transmission.

The cdma2000standard is a 3rd Generation (3G) solution based on theoriginal IS-95 standard. Unlike some other 3G standards, cdma2000is anevolution of an existing wireless standard. The cdma2000standardsupports 3G services as defined by the International TelecommunicationsUnion (ITU) for IMT-2000. 3G networks will deliver wireless serviceswith better performance, greater cost-effectiveness and significantlymore content. Essentially, the goal is access to any service, anywhere,anytime from one wireless terminal i.e. true converged, mobile services.

Worldwide resources are currently being devoted to roll outthird-generation CDMA technology. The cdma2000standard is one mode ofthe radio access “family” of air interfaces agreed upon by the OperatorsHarmonization Group for promoting and facilitating convergence of thirdgeneration (3G) networks. In other words, the cdma2000standard is onesolution for wireless operators who want to take advantage of new marketdynamics created by mobility and the Internet. The cdma2000 standard isboth an air interface and a core network solution for delivering theservices that customers are demanding today.

The goal of the cdma2000standard was to mitigate risks, protectinvestments and deliver significant performance boosts to operators asthey evolve their networks to offer 3G services. Networks based oncdma2000are backward compatible to cdmaOne (IS-95) deployments,protecting operator investments in cdmaOne networks and providing simpleand cost-effective migration paths to the next generation. In addition,cdma2000networks offer voice quality and voice capacity improvements,and support for high speed and multimedia data services.

The first phase of cdma2000—variously known as 1×RTT, 3G1×, or justplain 1×—offers approximately twice the voice capacity of cdmaOne,average data rates of 144 kbps, backward compatibility with cdmaOnenetworks, and many other performance improvements. The cdma2000 1×RTTstandard can be implemented in existing spectrum or in new spectrumallocations. A cdma2000 1×RTT network will also introduce simultaneousvoice and data services, low latency data support and other performanceimprovements. The backward compatibility with cdmaOne provided bycdma2000further ensures investment protection.

However, the cdma2000standard is evolving to continually support newservices in a standard 1.25 MHz carrier. In this regard, the evolutionof CDMA2000 beyond 1×RTT is now termed CDMA2000 1×EV or 1×EV for short.1×EV is further divided into two stages: 1×EV-DO and 1×EV-DV. 1×EV-DOstands for 1×Evolution Data Only. 1×EV-DV stands for 1×Evolution Dataand Voice. Both 1×EV evolution steps provide for advanced services incdma2000using a standard 1.25 MHz carrier. The evolution ofcdma2000will, therefore, continue to be backwards compatible withtoday's networks and forward compatible with each evolution option.

The 1×EV-DO standard is expected to be available for cdma2000operatorssometime during 2002, and will provide for even higher data rates on1×systems. Specifically, 1×EV-DO specifies a separate carrier for data,and this carrier will be able to hand-off to a 1×carrier if simultaneousvoice and data services are needed. By allocating a separate carrier fordata, operators will be able to deliver peak data transmission rates inexcess of 2 Mbps to their customers.

It is envisioned that 1×EV-DV solutions will be available approximatelyone and a half to two years after 1×EV-DO. A goal of 1×EV-DV is to bringdata and voice services for cdma2000back into one carrier. That is, a1×EV-DV carrier should provide not only high speed data and voicesimultaneously, but should also be capable of delivering real-timepacket services.

In summary, then, the cdma2000 1×RTT standard is optimized for voice andprovides basic packet data services up to 163.2 kbps. This standard iscurrently being commercialized and will be in the market very soon ifnot already. The cdma2000 1×EV-DO standard is optimized for data onlyand provides efficient data service up to 2 Mbps. This standard is to bedeployed after cdma2000 1×RTT. Finally, a proposed cdma2000 1×EV-DVstandard is to be optimized for both data and voice. Providingsimultaneous voice and data services, the goal of such a standard is toprovide more spectrum efficiency. Therefore, in terms of the evolutionpath of the cdma2000 standards for wireless high-speed datatransmission, the cdma2000 1×RTT standard is currently progressingtowards a cdma2000 1×EV-DO standard which is, in turn, progressingtowards an optimized cdma2000 1×EV-DV standard.

In examining the migration path from the 1×RTT standard to 1×EV-DO,those skilled in the art will appreciate that High Data Rate (HDR)technology served as the base technology for 1×EV-DO. Furthermore, theincorporation of the 1×RTT reverse link in 1×EV-DO achieved theobjectives of technology reuse as well as providing a cost-effectivesolution.

In a similar manner, a graceful evolution from 1×EV-DO to 1×EV-DV willminimize re-investments and avoid fragmenting the industry. In thislight, 1×EV-DV should be backward compatible to the 1×RTT family ofstandards and products. In other words, customer and operatorinvestments in CDMA systems should be protected. There should be maximumreuse whenever possible and the 1×EV-DV standard should also considerpossible future evolutions such as packet voice.

In addition to the above, any 1×EV-DV proposal should meet the CDMADevelopment Group (CDG) and Operator's requirements. Specifically,1×EV-DV should support services with various QoS attributes,simultaneous voice and data on the same carrier, voice capacityenhancement, more spectrum efficiency in packet data transmission andscalability to 3×mode operations.

1×EV-DO increases data capacity but does not allow for voice on the samecarrier and therefore does not change the voice capacity of thecdma2000family. Voice traffic must continue to use 1×RTT. As of Oct 22,2001 1×EV-DV proposals have integrated voice and data but voice ishandled in the same fashion as 1×RTT thus the voice capacity isunchanged.

SUMMARY OF THE INVENTION

A first broad aspect of the invention provides a method of transmittingover a forward link in a CDMA (code division multiple access)communications system. The method involves transmitting forward linkframes, each frame comprising a plurality of slots; for each slot,transmitting a forward shared channel, the forward shared channel beingadapted to have up to a predetermined maximum number of Walsh covers,and the forward shared channel being scheduled slot-wise to carry insome slots content for a single high-rate data user, in some slotscontent for a plurality of voice users (a voice user being voice orlow-rate data); and transmitting a user identification channel adaptedto allow users to determine which slots contain their content.

Preferably, the forward shared channel is further adapted to havescheduled in some slots content for a plurality of voice users and asingle high-rate data users.

In some embodiments, the user identification channel is transmitted inparallel with the shared channel using a different code space.

Preferably, during each slot the forward shared channel is scheduledover a number of Walsh covers equal to the predetermined maximum numberof Walsh covers minus a number of Walsh covers necessary to accommodatelegacy users being serviced during the slot.

The Walsh covers in some embodiments are 16-ary Walsh covers and in agiven slot, one or more of the 16-ary Walsh covers is furthersub-divided for the plurality of voice users, with all remaining 16-aryWalsh covers of the forward shared channel being assigned to a shareddata channel which is made available to a single high-rate data user ata time.

Preferably, each slot has a 1.25 ms slot duration, with the shared datachannel content for a given user may occupy multiple contiguous slots.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in further detail by way of examplewith reference to the attached drawings in which:

FIG. 1A is a network schematic for a first embodiment of the invention;

FIG. 1B is an example forward channel structure for use in the forwardlink of FIG. 1A;

FIG. 1C is an example forward voice traffic channel structure for usewith the forward channel structure of FIG. 1B;

FIG. 1D is an example forward data traffic channel structure for usewith the forward channel structure of FIG. 1B;

FIG. 1E is an example preamble channel structure for use with theforward channel structure of FIG. 1B;

FIG. 1F is an example power control and reverse activity channelstructure for use with the forward channel structure of FIG. 1B;

FIG. 1G is an example forward pilot channel structure for use with theforward channel structure of FIG. 1B;

FIG. 2 is a first example of a forward link slot structure provided byan embodiment of the invention;

FIG. 3 illustrates an example of how content might be scheduled usingthe slot structure of FIG. 2;

FIG. 4 is a second example of a forward link slot structure provided byan embodiment of the invention;

FIG. 5A is an example set of physical layer parameters for data on theforward link;

FIG. 5B is an example set of physical layer parameters for voice on theforward link for users having a high channel estimate;

FIG. 5C is an example set of physical layer parameters for voice on theforward link for users having a medium channel estimate;

FIG. 5D is an example set of physical layer parameters for voice on theforward link for users having a low channel estimate;

FIG. 6 is a channel summary for another CDMA forward link structureprovided by an embodiment of the invention;

FIG. 7 is a slot structure of a forward link structure in which thereare no legacy users;

FIG. 8 is a slot structure of a forward link structure in which thereare legacy users;

FIG. 9 illustrates an example set of Walsh separation codes for theforward link structures of FIGS. 7 and 8;

FIG. 10 is a block diagram of an example forward shared channelstructure for data and full rate voice;

FIG. 11 is a block diagram of an example forward shared channelstructure for non-full rate voice;

FIG. 12 is an example set of forward link shared channel voiceparameters;

FIGS. 13 and 14 are example sets of forward link shared channel dataparameters;

FIG. 15 is a block diagram of an example user identification channelstructure;

FIG. 16 is a block diagram of an example supplementary paging channelstructure;

FIG. 17A is a channel summary for CDMA reverse link structure providedby an embodiment of the invention;

FIG. 17B is a block diagram of an example reverse CHESS channelstructure;

FIG. 18 is a block diagram of an example reverse data ARQ channelstructure;

FIG. 19 shows an example structure for the reverse pilot channel;

FIG. 20 is a reverse link timing diagram;

FIG. 21A is a block diagram showing reverse channel I and Q mapping;

FIG. 21B is a block diagram of the reverse advanced access/commoncontrol channel;

FIG. 21C is a block diagram of the reverse traffic/dedicated controlchannels;

FIG. 22 is an example lower rate set of reverse supplementary channelcoding and modulation parameters; and

FIG. 23 is an example higher rate set of reverse supplementary channelcoding and modulation parameters.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1A shows a system schematic of an example wireless system in whichvarious embodiment of the invention may be employed. A base station (BS)160 is shown having three coverage area sectors 162,164,166. The basestation 160 forms part of a larger wireless access network (not shown).Different numbers of sectors may be employed. By way of example, shownare two wireless terminals (WT) 168,170 in sector 162, although a sectormay serve more than two wireless terminals. There is a shared forwardlink generally indicated by 172 used for transmissions from the basestation 160 to wireless terminals 168,170. Each wireless terminal alsohas a respective dedicated reverse link 174,176. Both the forward link172 and the reverse links 174,176 employ CDMA fundamentals.

A first embodiment of the invention provides a forward link designemploying CDMA (code division multiple access) technologies in whichtime division multiplexing is employed between data and controlinformation on the forward link to service multiple users per slot. Thefirst embodiment will be described with reference to FIGS. 1 to 5.Preferably, this design may be employed as a forward link portion of a1×EV-DV solution. Another embodiment of the invention provides a forwardlink design employing CDMA (code division multiple access) technologiesin which code division multiplexing between data and control informationis employed on the forward link to service multiple users per slot,which is preferably backwards compatible with legacy standards such asIS2000A. This embodiment will be described below with reference to FIGS.6 to 16. Preferably, this design may be employed as a forward linkportion of a 1×EV-DV solution. Either of the forward link designs may beused in combination with a reverse link design provided by anotherembodiment of the invention which is preferably also suitable as an1×EV-DV reverse link solution. The reverse link is described in detailbelow with reference to FIGS. 17 to 23. The reverse link design ispreferably similar to that now standardized in 1×RTT for example butwith some refinements. This allows for a significant reuse of existinghardware and software, while at the same time providing excellent dataperformance.

Preferably, for all embodiments, a 20 ms physical layer frame length isused for both the reverse link and the forward link. This is consistentwith 1×RTT. Advantageously, this frame size would allow a tri-mode modemcapable of supporting IS-95, I×RTT and 1×EV-DV. Also, in the discussionwhich follows, where the terms “voice” or “voice user” are used, this isintended to refer to any low rate users, namely users requiring thetransmission of voice data per se or to users having a data rateequivalent to the data rate required for voice information, i.e. datausers requiring a relatively low data rate.

An objective of wireless access network Radio Link Protocol (RLP) ARQschemes is to provide improved radio link quality by implementing aretransmission mechanism for all the services and applications. Theseembodiments of the invention provides a new ARQ mechanism for voiceservices in packet wireless communication systems.

There are two types of the services which may be provided. One type ofservice provides for delay-sensitive services, such as voice service.The other type of service provides for non-delay-sensitive service, suchas data services.

For the voice services, as will be detailed below, a base station maysend signals to multiple wireless terminals in one slot, each wirelessterminal receiving a packet during the slot. In response to this,multiple wireless terminals will send an ARQ signal back to the basestation to indicate if they received the packets correctly or not. Forhigh-rate data services, a single user will receive data during a givenslot. Two methods of achieving this are provided.

Forward Link—Time Division Multiplexed Control Implementation

Details of a first implementation of forward link 172 of FIG. 1 will nowbe provided with reference to FIGS. 1 to 5. The new forward link designallows for the efficient use of resources through the use ofmultiple-user forward link slots. The forward link employs a preamblethat allows multi-user packets on the forward link. This results inefficient allocation of forward link slots for voice and data servicefor multiple users.

The forward link is time multiplexed, with 20 ms frames consisting of 16slots with 1.25 ms per slot. Each slot contains 1536 chips. Transmissionstarts from one of the 16 slot boundaries. As will be described indetail below, each slot will support multiple users.

The forward link time-multiplexes a forward pilot channel, a forward MACchannel, and forward traffic channel(s).

The forward pilot channel is transmitted by each sector in each halfslot on the forward channel. Each pilot channel transmission consists ofunmodulated BPSK transmitted as 96 chip bursts every half slot at fullsector power.

The pilot channel is used for acquisition, synchronization,demodulation, decoding and C/I estimation by all wireless terminals inthe coverage area. By transmitting the pilot burst wise in this fashion,a sufficiently accurate C/I estimation can be obtained for data ratecontrol generation and adaptive modulation and coding. Pilot bursts fromall of the sectors are transmitted at the same time to facilitate C/Iestimation.

Referring to FIG. 2, shown is where in the slot the pilot bursts aretransmitted for two modes, namely an active mode during which forwardlink data is being transmitted, generally indicated by 100, and an idlemode during which forward link data is not being transmitted, generallyindicated by 102.

In active mode 100, a slot on the forward link (1.25 ms, 1536 chips)comprises a first 304 chip data period 104, a first 32 chip MAC channelslot 106, a 96 chip pilot burst 108, a second 32 chip MAC channel slot110, second and third 304 chip data periods 112,114, a third 32 chip MACchannel slot 116, a second 96 chip pilot burst 118, a fourth 32 chip MACchannel slot 120, and a fourth 304 chip data period 122. In the inactivemode 102, the MAC channel slots 106,110,116,120 and pilot bursts 108,118 are transmitted at the same time during the slot as was the case forthe active mode, with the no data transmission during the data periods.

The forward MAC channel carries a reverse power control (RPC) channeland a reverse activity (RA) channel.

The forward traffic channel is provided over the four data periods104,112,114,122, and is used to provide for different services withvarious QoS attributes, such as real time data, non-real time data, etc.In some slots, one or more of these data periods 104,112,114,122 areused to transmit a preamble which identifies which users are beingscheduled during the slot.

Referring again to FIG. 2, the data periods 104,112,114,122 are used fora time division multiplexed forward traffic channel, the time divisionmultiplexing occurring between data transmission, and pilot and MACchannel slot transmission. Advantageously, this allows a higher numberof users per slot with modest rate requirements, or a modest number ofhigh-rate voice and data users.

During the data periods 104,112,114,122, a number of CDMA Walsh coversare used to transmit forward traffic channels. Preferably, 16 16-aryWalsh covers are used. The Walsh covers are allocatable on a per slotbasis such that a single slot is adapted to serve multiple low data rateor voice users so as to provide efficiency and flexibility, and up toone high data rate user.

Each slot is either a multi-user slot, or a single high-rate user slot.For a single user slot, all 16 Walsh covers are used to transmit data tothe single high-rate user. In a multi-user slot, the 16 Walsh covers areallocated between up to 16 users, with one, two or four Walsh covers peruser.

Each multi-user slot has a preamble which identifies the users who arebeing scheduled during the slot. Single user packets may be transmittedover multiple slots, and the first of such multiple slots contains apreamble identifying the data user and transmission parameters for thedata packet.

The base station schedules data packets onto the forward traffic channelbased on channel estimates fed back over the CHESS channel received fromwireless terminals on the reverse link, QoS requirements and trafficload at the base station. The base station must schedule at least onevoice frame onto the forward traffic channel for each simultaneous voiceand data user within one 20 ms frame. The actual rate for a single userslot is specified by an EDRI (explicit data rate indicator).

FIG. 3 illustrates an example slot scheduling breakdown for a multi-userslot 960 and a single user transmission 962 composed of two slots964,966. All three slots 960,964,966 have the a pair of respective pilotperiods, and four respective MAC channel slots. Multi-user slot 960 hasa multi-user preamble 968 which in this example identifies (through userindex construct, described below) four voice users each occupying 4Walsh codes. The transmissions for the four voice users are indicated asV1, V2, V3 and V4. For the single user transmission, the first slot 964contains a preamble 970 which identifies (through the group IDconstruct) the data user. The entire traffic capacity of the slot 964and the following slot 966 is dedicated to the single user as indicatedby D1 in both slots.

It is to be understood that other field sizes may alternatively beemployed for the MAC channel slots, pilot and data periods. Anotherexample is shown in FIG. 4 for both active and idle modes where in a1536 chip slot, there are be two 348 chip data periods 140,144, two 72chip pilot bursts 142,150, two 64 chip MAC channel slots 148,152, andtwo 284 chip data periods 146,154.

The forward channel structure is shown in FIG. 1B. The forward trafficor control channel inputs C,D, the preamble and ERDI inputs E,F, thepower control and RA channel inputs G,H and the pilot channel inputs K,Lare input to TDM (time division multiplexing) block 800 which performstime division multiplexing as shown in FIG. 2 for example. Quadraturespreading is performed at block 802. I and Q outputs are basebandfiltered 804,806, modulated at 810,812 and then summed together at 814to produce a forward modulated waveform.

The forward voice traffic channel structure is shown in FIG. 1C. A voiceuser may be assigned more than one Walsh cover, and preferably one, twoor four Walsh covers. A voice user input is channel encoded 830, with an8K or 13K encoder for example. Then scrambling, sequence repetitionand/or symbol puncturing is performed at 832. Next, QPSK or 16 QAMmodulation is performed 834. Walsh cover is applied 836 and Walshchannel gain applied 838. Finally, the outputs thus produced for all thevoice users are summed with Walsh Chip level summer 840. Outputs C and Dare inputs to the forward channel structure of FIG. 1B.

The forward single user data traffic channel structure is shown in FIG.1D. Forward data traffic channel physical layer packets are encoded withR=⅓ or ⅕ rate encoder 860. A scrambler 862 sequence is added at 863.Then channel interleaving is employed 864 and modulation is performed byQPSK/8PSK or 16 QAM modulator 866. Symbol repetition and/or symbolpuncturing is performed at 868. Symbol demultiplexing 16 to 1 occurs at870. Then the appropriate Walsh cover is applied for each of the sixteenchannels at 872, Walsh channel gain applied at 873, and Walsh chip levelsumming occurs at 874. Outputs C and D are inputs to the forward channelstructure of FIG. 1B.

The preamble channel structure is shown in FIG. 1E. The preambleinitially consists of all 0's. This is signal mapped at 880. Then, a 32symbol bi-orthogonal cover with user index/Group ID i is applied at 882.Sequence repetition is performed at 884, and a preamble gain applied at886. For the EDRI, 8-ary orthogonal modulation is applied at 888, signalmapping occurs at 890, sequence repetition occurs at 892, and an EDRIchannel gain applied at 894. Outputs E and F are inputs to the forwardchannel structure of FIG. 1B. The EDRI indicates the coding andmodulation employed for the single high-rate user.

There are 32 Walsh×2 (plus,minus) possible bi-orthogonal codes which maybe applied to the preamble structure above, thereby allowing theidentification of 64 different user index/Group ID.

The preamble channel structure used in multi-user slots is shown in FIG.1E, but no EDRI is required.

Each data user has a single Group ID for their data service (this beinganalogous to user index I), and this is transmitted during the preambleof a single user slot as indicated above in the discussion of FIG. 1B.Each voice user has three Group IDs, one GID1 for use when its voice istransmitted using one 16-ary Walsh cover, one GID2 for use when itsvoice is transmitted using two 16-ary Walsh covers, and one GID4 for usewhen its voice is transmitted using four 16-ary Walsh covers. Each userhas Walsh covers assigned to it for each of the its three Group IDs,i.e. for GID1 the user is assigned one Walsh cover, for GID2 the user isassigned two Walsh covers, and for GID4 the user is assigned four Walshcovers. Multiple users may be assigned the same GIDs. When a given GID1is transmitted, then all voice users having been assigned GID1 will knowto expect a voice packet on the single Walsh cover associated with GID1Similarly, when a given GID2 is transmitted, then all voice users havingbeen assigned GID2 will know to expect a voice packet on the two Walshcovers associated with GID2, and when a given GID4 is transmitted, thenall voice users having been assigned GID4 will know to expect a voicepacket on the four Walsh covers associated with GID4. The preamblefunctions as a user identification channel, allowing users to determinewhether a given slot contains any content for them.

The structure of the MAC channel slots 106,110,116,120 is designed tofacilitate this denser and more flexible packing of users down to thesub-slot level. The structure of the MAC channel which is used to carryreverse power control commands and reverse activity commands is shown atFIG. 1F. RPC bits for user ID i are signal mapped 900. Then RPC Walshchannel gain is applied at 902. A 64-ary Walsh cover is applied at 904.RA bits, 1 per 8×RABLength slots (100/RABLength bps) are input to bitrepetition block 908 with repetition factor equal to RABLength. Then,signal point mapping occurs at 910 and an RA channel gain is applied at912. A 64-ary Walsh cover is applied at 914. The outputs of 904 and 914are summed with Walsh chip level summer 906 which has an output which issequence repeated 916. Outputs G and H are inputs to the forward channelstructure of FIG. 1B. The MAC channel provides one PC bit per slot forup to 63 users and one RA bit per slot. A first state of the RA bitindicates to all users transmitting on the reverse link that things arefine as they stand, and a second state of the RA bit indicates to allusers transmitting on the reverse link that there is too much activityon the reverse link and that data rates should be lowered.

Finally, the pilot channel structure is shown in FIG. 1G. Here, thepilot channel bits which consist of all 0's, are signal mapped at 930and then the Walsh cover 0 is applied at 932. Outputs K and L are inputsto the forward channel structure of FIG. 1B.

The forward link physical layer parameters for data are shown in FIG.5A. Data packets can be from 1 to 16 slots in length the preamble forthe different possibilities also varies from being as small as 128 chipsto as large as 1024 chips. When the preamble is longer, the userindex/group ID for the data user is repeated.

The forward link physical layer parameters for voice are shown in FIG.5B, 5C and 5D for users having high, medium and low channel estimatesrespectively. In FIG. 5B, the parameters are used when there are 16voice users, with one Walsh code per user. FIG. 5C shows the parametersused when there are eight users with two Walsh codes per user. FIG. 5Dshows the parameters used when there are four users with four Walshcodes per user.

Forward Link—Code Division Multiplexed Control Implementation

Another embodiment of the invention provides a forward link design inwhich control is multiplexed with data using code multiplexing. Thisembodiment will now be described with reference to FIGS. 6 to 16. Thenew channel breakdown for the forward link is shown in FIG. 6. Theforward channels include:

-   Forward Pilot Channel (F-PICH) 250;-   Forward Sync Channel (F-SYCH) 252;-   TDPICH channel 254;-   Supplemental Paging Channel (F-SPCH) 258;-   Quick Paging Channel 1 256;-   Quick Paging Channel 2 257;-   Forward Paging Channel (F-PCH) 260;-   User identification channel (UICH) 262;-   Forward Shared Power Control Channel (F-SHPCCH);-   Common Explicit Data Rate Indication Channel (CEDRICH) 266; and-   Shared Channel (SHCH) 268.

Preferably, the pilot channel 250, sync channel 252, TDPICH channel 254,quick paging channels 256,257, and paging channel 260 have the samechannel structure as the corresponding channels as defined by IS2000A.Furthermore, preferably, the shared power control channel 264 has asimilar structure to the CPCCH (common power control channel) providedby IS2000A, with differences noted below. Each of the channels which arenot based on IS2000A are described in detail below.

Forward Link Operation.

The forward link uses code division multiplexing within time divisionmultiplexing on a new shared channel (SHCH). The SHCH allows flexibleslot scheduling and slots with multiple voice users and up to one datauser. Forward link transmission is organized as 20 ms frames. Each frameconsists of sixteen 1.25 ms slots. Each slot contains 1536 chips.

The slot structure of the forward link depends upon whether service isto be provided to legacy IS95/1×RTT users. A forward slot/code structureis shown in FIG. 7 for the case where it is assumed there are noIS95/1×RTT users. Effectively, there are 16 Walsh length 16 code spacesubchannels.

The slot structure contains the following channels: Forward PilotChannel (F-PICH) 250 having a Walsh length of 64 chips, Forward SynchChannel (F-SYCH) 252 having a Walsh length of 64 chips, the TDPICHchannel 254 having a Walsh length of 128 chips, the supplemental pagingchannel F-SPCH 258 having a Walsh length of 128 chips. The slotstructure has quick paging channels 256,257 each having a Walsh lengthof 128. Channels 250,252,254,256,257 and 258 collectively effectivelyoccupy one Walsh 16 code space. The slot structure also has ForwardPaging Channel (F-PCH) 260 having a Walsh length of 64 chips, and eightuser identification channel (UICH) 262 each having 8 subchannels andWalsh code of length 512 chips, for a total of 64 UICH subchannels. Ifadditional user identification channel capacity is required, thenadditional Walsh codes can be assigned code space permitting. Space mayalso be taken from the shared channel if necessary. The slot structurefurther includes three Forward Shared Power Control Channels (F-SHPCCH)264 each having 24 subchannels and a Walsh length of 128 chips, giving atotal of 72 power control bits per slot capacity since for each of thethree code channels, 24 power control bits can be time divisionmultiplexed and transmitted. Preferably, two of the power control bitsare used by the Reverse Activity (RA) channel, which are used tobroadcast reverse activity commands and can be used for reverse linkrate control. It is noted that six bits of the FSPCCH are preferablyused for the advanced access channel described in applicant's copendingapplication. If additional power control subchannels are required, thenextra code space may be allocated for this purpose. The slot structurealso has a common explicit data rate indication channel (CEDRICH) 266which has four Walsh codes of length 512 chips. Channels 260,262,264 and266 collectively effectively occupy one Walsh 16 code space. Finally,the shared channel (SHCH) 14 which occupies 14 Walsh 16 code spaces. Adetailed example breakdown of the Walsh separation is provided in thetable of FIG. 9.

In the event there are IS95/1×RTT (legacy) users which need to besupported, the slot structure of FIG. 7 easily adapts to allow this. Asubset of the capacity of the shared channel 268 can be used for theselegacy users. An example is shown in FIG. 8 for the case where it isassumed there are IS95/1×RTT users. The slot structure is the same asthat of FIG. 7 down until the shared channel. The slot structure of FIG.8 has two 1×RTT voice channels 270,272 each having a Walsh length of128, one 1×RTT data channel 272 having a Walsh length of 32, and oneIS95 voice channel 276 having a Walsh length of 64, these legacychannels collectively occupying one Walsh 16 code space which was takenfrom the capacity formerly allocated to the shared channel leaving asmaller Shared Channel (SHCH) 278 is which occupies 13 Walsh code spacesrather than 14 as was the case for the Shared Channel of FIG. 7.Depending on the number of legacy users at a given time, the size of theshared channel 278 can shrink, potentially down to zero, or grow back tothe maximum 14 Walsh code spaces nominally allocated.

Forward link Shared Channel (SHCH)

The shared channel 268 is a very flexible channel. The shared channel,in this example, may have up to 14 16-ary Walsh codes.

In one embodiment, each SHCH 1.25 ms slot is assignable on a TDM basisfor a combination of voice users plus a single data user, or for asingle high-rate data user.

The assumption being made is that the high-rate data user does notrequire real time traffic delivery. For a given user, it is acceptableto wait until enough information has built up to fill an entire slot forthe user and/or to wait until the channel to the given user is good.

In one embodiment, the SHCH has a fixed bandwidth. In anotherembodiment, the SHCH has a bandwidth equal to a maximum bandwidth minusa bandwidth required to service legacy voice and low-rate data users.More specifically, in this embodiment space on the shared channel 268can be taken as needed to support legacy voice and data channels,thereby reducing the size of the shared channel 268.

Nominally, the shared channel is scheduled on a 1.25 ms basis. However,for high rate data users, longer scheduling periods of 1.25, 2.5 and 5msec may be allowed.

A data-only SHCH slot has all 14 available 16-ary Walsh codes allocatedto a single user's data. Alternatively, if some of the SHCH 16-ary Walshcodes have been allocated for legacy traffic, then a data-only SHCHpreferably uses all the remaining SHCH 16-ary Walsh codes.

A hybrid SHCH slot has the 14 available 16-ary Walsh codes (or whatevernumber are available after servicing legacy users) split between one ormore voice users and up to one data user. Voice users may take up all ofthe SHCH 16-ary Walsh codes.

A number of different modulation and coding schemes are preferablysupported for voice users as summarized in FIG. 12 including full, half,quarter and eighth rate. Full rate voice uses Turbo coding and can useeither one or two SHCH 16-ary Walsh codes depending upon the channelestimates (CHE) fed back to the base station and other factors. Half,quarter and eighth rate voice uses convolutional coding and uses onlyone SHCH 16-ary Walsh code. The wireless terminal must blindlydistinguish between the five possibilities based on getting the correctCRC. Per voice user gain is also adjusted based on the CHE.

A number of different modulation and coding schemes are also supportedfor the high rate data user as summarized in the tables of FIGS. 13 and14. Other rates may also be supported. Data users adapt modulation andcoding based on the Channel Estimate (CHE) every 1.25 msec. Because thesize of the portion of the shared channel which may be dedicated to ahigh-rate user varies as a function of how many voice and legacy usersare also scheduled in the same slot, many different effective data ratesare required.

A preferred forward shared channel structure for a single high-rate datauser which is the same as that for a single full rate voice user isshown in FIG. 10 where it is assumed that the user has N Walsh codes.The single high-rate data user may have up to all N=14 Walsh codes,while the voice user will have either one or two Walsh codes. Physicallayer packets are encoded with ⅕ rate Turbo encoder 402 and then passthrough channel interleaver 404 and preferably processed by SPIRSS block405 and then modulated with modulator 406 (which may be QPSK, 8-PSK or16-QAM depending upon modulation type). The symbols thus produced are 1to N demuxed 416 and the appropriate long code is added, the long codebeing produced by applying the long code mask to a long code generator410 followed by decimator 412. Walsh channel gain is applied 420, andthe appropriate N Walsh covers 418 are applied. Finally Walsh chip levelsumming 422 occurs.

In one embodiment of the invention, the even second timing referenced toUTC (Universal Coordinated Time) is used to select the portion of the ⅕rate Turbo coded binary symbols to be transmitted over a given slot.Before describing this embodiment in detail, the following notations aredefined:

N is the user payload packet size in number of symbols;

M is the coded packet size, which is the packed size (in number ofsymbols) after ⅕ rate Turbo coding, M=5N;

L is the actual transmitted packet size in number of symbols. Theeffective coding rate is N/L.

In both the access network and the wireless terminal, there is a countreferenced to the even second. At the start of each even second, thecount is cleared to zero. Then for each four slots (i.e. every 5 ms),the count is increased by one. Since there are 1600 slots in one evensecond period, the count value can go from 0 to 399. For example, if thestarting position of the even second is aligned with the startingposition of slot 0 of the current frame, the count value at slot 0, 1,2, and 3 of the current frame would be 0. The count value at slot 4, 5,6, and 7 of the current frame would be 1. The count value at slot 8, 9,10, and 11 of the current frame would be 2. The count value at slot 12,13, 14, and 15 of the current frame would be 3. The count value at slot0, 1, 2, and 3 of the next frame would be 3 and so on.

The Turbo coded packet can be viewed as a periodic signal with theperiod equal to M. The actual transmitted packet will be selected fromthe periodic coded packet based on the count value at the current sloton which it will be scheduled on. If the packet to be transmittedrequires more than one slot, it will be selected from the periodic codedpacket based on the count value at the first slot.

Suppose that the count value at the current slot is k. The startingposition of the actual transmitted packet is calculated fromi1=1+(kL) modulo M.

The ending position of the actual transmitted packet is calculated fromi2=i1+L−1

When the wireless terminal receives the packet, it can derive the packetsize information (N, M, L) from the CEDRIC channel (described in detailbelow). From the count value at the slot the packet is received (or atthe first slot the packet is received if the received packet containsmultiple slots), it knows which portion of the ⅕ rate Turbo coded datapacket the received packet belongs to and decodes the packet in a properway. If the decoded result does not pass CRC, the wireless terminal willcheck if the previous received packet is decoded correct or not. If theprevious received packet is wrong, the current received packet will beused for soft combining and/or incremental redundancy with the previousreceived packet. If the previous received packet is correct or the jointdecoded result is wrong, a NAK signal is sent to the base station. Thecurrent received packet will be stored and may be used for softcombining and/or incremental redundancy with the future received packet.

A preferred forward shared channel structure for non-full rate voice isshown in FIG. 11. There is a channel structure instantiation for eachnon-full rate voice user. In FIG. 11, two such identical channelsstructure are shown 440,445. Channel structure 440 will be described byway of example. Physical layer packets are encoded with encoder 450 andthen pass through channel interleaver 452, and QPSK modulator 454. I andQ channels thus produced then undergo sequence repetition and/or symbolpuncturing 456. The appropriate long code is added, the long code beingproduced by applying the long code mask to a long code generator 458followed by decimator 460. The appropriate Walsh cover 462 is applied,Walsh channel gain 464 is applied, and finally Walsh chip level summing482 occurs.

SHCH and Hybrid SHCH slots are scheduled by the base station, andwireless terminals are informed of whether a given slot containsvoice/data for it using the User Identifier Channels (UICH).

A user identification channel (UICH) is a forward channel which providesa method of informing a wireless terminal of whether a current slot ofthe shared data channel contains his/her data. In a preferredembodiment, eight Walsh codes of length 512 are allocated for the UICHchannel. A user's identification transmitted on this channel consists ofa three bit sub-identifier transmitted using an I or Q component of oneof the eight Walsh codes. There are four different three bitsub-identifiers as follows:

Identifier 1: 000

Identifier 2: 010

Identifier 3: 110

Identifier 4: 101

In each slot, a sub-identifier is spread by a 512-ary Walsh code and canbe transmitted on either I or Q components. Since I and Q components canbe detected independently and eight Walsh codes are used for the UICH,there is a total of 64 users (8 Walsh codes×2 components×4sub-identifiers) which can be identified uniquely by the channel. Foreach slot, up to sixteen users can be identified. The UICH channelstructure is shown in FIG. 15. The mapping between a given user and aUICH identifier is set up each time a wireless terminal connects. Then,the sub-identifiers to be transmitted on the I and Q components areencoded with encoders 320,322, provided with channel gain with channelgain elements 324,326, and then Walsh code covered (not shown) andtransmitted.

The above described User Identifier Channels (UICH) indicate which useror users are scheduled in the current slot. Up to sixteen users may beidentified per slot. A user with simultaneous Data and Voice has oneUICH for Data and one UICH for Voice. The user is informed of itsUICH(s) when during initial signaling with the base station.

More generally, the sub-identifier is an N bit identifier, and the Walshcode is one of P M-ary Walsh codes. The user identification channel istransmitted in K chip slots, and has I and Q channels, thereby providingthe 2*K/(M) bit capacity, and the ability to transmit 2*K*M/N useridentifiers per slot. In the above example, M=512, K=1536, N=3 and P=8thereby providing the ability to transmit 16 user identifiers per slot,and the ability to uniquely identify 64 different users. In anotherspecific example, M=512, K=1536, N=3, P=16 thereby providing the abilityto transmit 32 user identifiers per slot, and the ability to uniquelyidentify 128 different users.

Preferably, voice users are scheduled in the first half frame (i.e. inthe first eight slots). An ACK signal is sent by a wireless terminal ifthe wireless terminal receives a voice packet correctly. When thewireless terminal decodes the UICH correctly and detects the signal bymeasuring its energy and the CRC of the received voice packet fails, aNAK signal is sent to the base station. Otherwise, no ACK or NAK signalwill be sent. When a NAK is received for a voice packet, the basestation will re-transmit the packet unless the voice rate is 1/8 rate inwhich case the voice packet is not retransmitted.

Voice users are assigned a voice channel number (V=0, 1, 2, . . . )which is used to calculate the one or two W16 codes on which it willreceive voice information. The supplemental paging channel SPCHbroadcasts the total number of 16-ary Walsh codes available (Nd) on theSHCH. For Data only SHCH slots, Nd will be the number of codes availableto the data user. Also broadcast is the number of 16-ary Walsh codesavailable for voice in hybrid SHCH slots (Nv). In a hybrid slot, therewould be Nd-Nv Walsh codes for the high rate data user. The W×116 andW×216 codes for a particular voice user are calculated by:X1=15−mod(V,Nv) and X2=15−mod(V+1,Nv)

Scheduling is performed on the basis of QoS commitments, the channelestimates received from the wireless terminals and sector select values.If a sector select erasure is received corresponding to a data user thenno data will be scheduled for that user. If a sector select erasure isreceived corresponding to a voice user then voice information willcontinue to be scheduled for that user. Two sector select valuescorresponding to another valid sector must be received before the activesector stops sending voice information.

A preferred structure for the SPCH is shown in FIG. 16. The SupplementalPaging Channel (SPCH) broadcasts Nd and Nv as detailed above. Thechannel bits containing this information are convolutionally encodedwith encoder 430, and interleaved with channel interleaver 432. A longcode mask generated by long code mask generator 434 and decimator 436 isapplied, and then channel gain 438 and demux functions 440 areperformed.

The Common Explicit Data Rate Indication Channel (CEDRICH) is used toindicate the coding/modulation format applied for data only use of theshared channel. Another embodiment of the invention provides thischannel used to determine the data rate for data transmitted on theShared Channel. Preferably, four Walsh codes of length 512 are used forthe channel.

The data rate can be determined from the number of Walsh codes used fordata, the data packet size and packet length. The Supplemental PagingChannel broadcasts the number of Walsh codes for the Shared Channel andthe number of Walsh codes used for voice when both voice and data aretransmitted in the Shared Channel in a single slot. The CEDRIC channelcarries the information of packet size, packet length and a slot typeflag indicating whether the slot is for one data-only user or formultiple data and voice users. To help wireless terminals to do highorder demodulation (64-QAM or 16-QAM), a gain value may be included inCEDRIC.

The CEDRIC is composed of three sub-channels. The first one (CEDRIC_a)carries the packet length in units of slots, and it is represented bythree symbols (1536 chips after spreading) transmitted in I component ofa Walsh code in a slot. The mapping between the symbols and packetlength is specified in Table 2.

Table 2. The mapping between the symbols and packet length

Packet Length (slots) Symbols 1 No energy 2 000 4 111

The second sub-channel (CEDRIC_b) carries information consisting of DataPacket Size and slot type flag for Low Order Modulation (QPSK and8-PSK). The third sub-channel (CEDRIC_c) carries information consistingof Data Packet Size and slot type flag and the gain value for high ordermodulation (64-QAM or 16-QAM).

Each sub-channel uses different Walsh codes. For low order modulations,one Walsh code is assigned to carry the packet size information. Twopacket sizes will be used if the packet is transmitted in one slot,therefore only one bit is needed to indicate the packet size (see Table3). One more bit (slot type flag) is needed to indicate whether the slotis for one data-only user or for multiple data and voice users (seeTable 4). Four packet sizes can be used when a packet is transmitted inmultiple slots and two bits are needed to indicate the packet size (seeTable 5). However, only data packets are transmitted in multiple slotsand thus the slot type flag is not needed. In summary, for both singleslot packets or multiple slot packets, two bits are encoded into sixsymbols, which are spread by a 512-ary Walsh code and transmitted on Iand Q components.

Table 3. Packet Size Indication for Single Slot Packets

Packet Packet Size Flag Size 0 3072 1 1536Table 4. Slot Type Indication for Single Slot Packets

Slot Type Flag Slot Type 0 Data only 1 MixedTable 5. Packet Size Indication for Multiple Slot Packets

Packet Size Flag Packet Size 00 3072 01 1536 10 768 11 384

For high order modulations, two and a half Walsh codes (half meaning theQ component of the Walsh code used for packet length) are assigned tocarry the packet size and the gain information. Similar to the low ordermodulation, a 1-bit packet size flag and a 1-bit slot type flag are usedfor single slot packets while a 2-bit packet size flag is used formultiple slot packets. Five bits are used to represent the gain. Allseven bits are encoded into fifteen symbols and are spread by 512-aryWalsh codes.

If a packet is transmitted in a single slot, the packet size, slot typeflag (and gain when applicable) will be transmitted in the same slotwith the data packet. If a packet is transmitted in multiple slots, thepacket length (number of slots) will be transmitted in the first slot.The packet size (and gain when applicable) will be transmitted in thefollowing slots. Effectively, only one sub-channel is transmitted in oneslot.

Shared Power Control Channels (SHPCCH) handle reverse link PC whenforward link uses SHCH. Details of a preferred implementation areprovided in Applicants below-referenced copending application.

The SHPCCH is used by the reverse advanced Access Channel (AACH).Predefined PC bits from the SHPCCH to acknowledge and to power controlwireless terminal pilots prior to message transmission from wirelessterminals during access probes.

Preferably, two bits are used to send a single reverse activity (RA)control bit repeated twice. A first state of the RA bit indicates to allusers transmitting on the reverse link that things are fine as theystand, and a second state of the RA bit indicates to all userstransmitting on the reverse link that there is too much activity on thereverse link and that data rates should be lowered.

NAK for Outer Loop Power Control

The base station adjusts the power transmitted to users on the basis ofthe channel estimate information fed back from the wireless terminals.Preferably, in another embodiment, NAK signals fed back from wirelessterminals are used to determine a measure of frame error rate, and thismeasure is used for outer loop power control, i.e. to change the mannerby which the channel estimates are mapped to base station transmissionpower. By counting the NAK and-no ACK/NAK frames, the base station cancalculate the forward link frame error rate. This error rate can then beused to make a decision in respect of outer loop power control. No othersignaling from the reverse link is needed for this outer loop powercontrol.

Reverse Link Operation

Details of a reverse link design provided by another embodiment of theinvention used for reverse links 174,176 of FIG. 1 will now be providedwith reference to FIGS. 17 to 23. Preferably, the reverse link is the1×RTT reverse link with the addition of a new channel for feeding backchannel estimates and sector selections, new channels for ARQ feedbackand reverse rate indication, and a modified reverse supplementarychannel having the data rate indicated by the Reverse Rate Indication(RRI) channel. Each 20 ms reverse link frame consists of 16 1.25 msslots or power control groups. Code channels are used for multiplexing(fundamental, supplemental channels). A frame offset is applied torandomize the reverse link transmissions.

Referring now to FIG. 17A, the reverse link has the following channels:

a reverse pilot channel (R-PICH) 272;

reverse MAC channels consisting of the R-CHESS (reverse channel estimateand sector select) channel 270, RRI (reverse rate indicator) channel282, reverse data ARQ (R-DARQ) channel 276, reverse voice ARQ (R-VARQ)channel 274;

reverse traffic channels which include reverse fundamental channel(R-FCH) 278 (for voice traffic) and reverse supplemental channel (R-SCH)280 (for data traffic);

reverse advanced access channel (R-AACH) 288;

reverse dedicated control channel (R-DCCH) 284; and

reverse common control channel (RCCCH) 286.

Each of the reverse link channels will now be detailed in turn withreference to FIG. 20 which is a reverse link timing diagram showing howthe timing of the various reverse link channels relates to that of theforward channels slots as received by a wireless terminal. Forward linktraffic is transmitted over 20 ms frames containing 16 1.25 ms forwardchannel slots 190. T0 is the frame boundary at the wireless terminalwith an assumed round trip delay of 0. Of course there would be anon-zero round trip delay which would increase as a function of awireless terminal's distance from the base station. This would have theeffect of delaying all of the reverse link timing with respect to theactual forward link slot timing, but not with respect to the forwardlink slots as received at a given wireless terminal.

Reverse Pilot Channel, RRI Channel, and VARQ Channel

The reverse link MAC is composed collectively of the fast reverse VARQchannel 274, reverse DARQ channel 276, RRI channel 282 and R-CHESSchannel 270 (described in detail below). The structure of the pilotchannel is preferably the same as the 1×RTT reverse link pilot channel.The last 384 chips of every 1.25 msec slot contains a single bit ofinformation. For 1×RTT this bit is a power control bit. For thisembodiment of the invention this bit is instead used to communicate VARQand RRI. The pilot channel is used by the BS as a phase reference, forchannel estimation and for the reverse link power control.

The reverse pilot channel 194 is the same as the 1×RTT reverse pilotchannel when operating in backward compatible mode. In backwardscompatible mode, the wireless terminal is a legacy wireless terminal. Inthis embodiment of the invention, rather than providing anotherdedicated ARQ channel for VARQ for each wireless terminal, the powercontrol bits (PCB) of the pilot signals in the 1×RTT reverse linkstructure are replaced by a reverse rate indicator (RRI) and ARQ forvoice services. When the wireless terminal used the forward sharedchannel for the forward link, then each pilot channel 194 slot containspilot, RRI, and VARQ fields as described in detail below. The timing ofthe reverse pilot channel is shown in FIG. 20 and is slightly differentdepending on whether voice only indicated generally at 194, or voice anddata is being transmitted indicated generally at 202. In both cases, thereverse pilot channel 194,202 is aligned with the forward channel slots,so there are 16 1.25 ms slots.

The reverse link pilot channel is summarized at a very high level inFIG. 19. Again, this is similar to the 1×RTT reverse pilot channelexcept that the power control bits are now replaced by RRI (reverse rateindicator) and Voice ARQ (VARQ) bits. The pilot channel over one slotcontains a pilot period 180 during which 1152 pilot chips are sent, anda period 182 during which the PCB/RRI/VARQ is sent over 384 chips, PCBbeing sent by legacy terminals. During an entire frame, there are 16 bitpositions available through the collective use of period 182 from 16slots (formerly used for power control) which are now used for RRI/VARQ.

Case 1: Voice Only Users

For the voice only users, the position of the ACK or NAK bit is notfixed. Slots 2, 6, 10 and 14 are reserved for RRI. A single RRI bit ismapped to all 4 bit positions to indicate the use of the fundamentalchannel and dedicated control channel. Setting all four RRI bits to “0”in -one frame indicates that there is only fundamental channel beingtransmitted. Setting all four bits in one frame to “1” indicates thatthe DCCH and fundamental channel are being transmitted.

If a user's voice data is decoded correctly, the ACK VARQ signal will besent to the base station in all the slots in the frame. If nothing wastransmitted for the user in a given slot, or if the user's voice data isdecoded incorrectly, then a NAK VARQ signal will be sent to the basestation. Preferably, a “1” is sent to indicate an ACK, and a “0” is sentto indicate a NAK. The possible positions of the VARQ signals are inslots 3,4,7,8,9,11,12,13 and 15 of the current frame and slots 0 and 1of the next frame. For a Forward traffic channel voice frame transmittedin slot n of the forward channel, the corresponding ACK channel bit istransmitted in slots n+2 and any following remaining slots in the frameand slots 0 and 1 of the following frame.

An example of this can be seen in the timing diagram of FIG. 20 where itis assumed a forward voice packet for a voice only user is sent to agiven wireless terminal during slot n 204. After slot n and slot n+1 arereceived, slot n+2 containing an RRI bit 208, the VARQ is included inthe RRI/VARQ bit in the reverse pilot channel 194 during the followingthe remaining non-RRI slots of the frame, including for example slots206,207 and during the first two slots of the next frame (not shown).

Case 2: Voice and Data Users

The timing of the VARQ for voice plus data users is shown in FIG. 20indicated generally at 202. In this case, 14 PC bits in one frame willbe used for RRI to indicate the rate being used on the reversesupplemental channel. Preferably, each RRI symbol (3 bits) is mapped toa simplex code with a length of seven, repeated twice, mapped toRRI/VARQ locations 0 to 8 and 11-16. The RRI is used to indicate whetherthe dedicated control channel or supplemental channel or neither isactive for the current frame. The three bit RRI symbol can take one ofeight values, one value (preferably 0) indicating that there is no DCCHand no supplemental channel, one value (preferably 1) indicating thatthe DCCH only is being transmitted, and remaining values 2 through 7indicating supplemental channel only, and indicating a particular ratefor the supplemental channel. The rates are detailed below under thediscussion of the supplemental channel with reference to FIGS. 22 and23.

The VARQ signals are transmitted in fixed positions at the 9th and 10thslots 203,205. If the user's data is correctly decoded, the ACK VARQsignal will be sent. Otherwise, a NAK VARQ signal will be sent to basestation.

Data ARQ

For data ARQ, the data ARQ channel 196 is used by data or voice and datausers which is also aligned with the forward channel slots, so there are16 1.25 ms slots. An ACK signal is sent to the base station if thewireless terminal receives a data packet correctly. When the wirelessterminal detects the proper UICH and the CRC of the received data packetfails, a NAK signal is sent to the base station. When the wirelessterminal does not detect the proper UICH then no ACK or NAK signal willbe sent. The DARQ signals for data are sent using the DARQ channel inthe first half slot starting two slots after the end of the data packetis received at the wireless terminal. An example of this is shown inFIG. 20 where a data packet has been transmitted on slot n, and the DARQ197 is sent on the R-DARQ channel 196 in the first half slot of slotn+3.

The structure of the reverse DARQ channel is shown in FIG. 18. DARQtakes one bit per slot in first ½ slot, employs bit repetition 600,signal point mapping 602 and Walsh cover 604.

Reverse Link Supplemental Channel and Fundamental Channel

The reverse supplemental channel has a variable data rate from 4.8 kbpsto 1228.8 kbps. The fundamental channel is supported for voice, withpreferably both 1×RTT 8k and 13k vocoders being supported as well as anew 8k vocoder with turbo coded full rate voice. Simultaneous voice anddata can be transmitted. The variable data rates are determined by thewireless terminal in cooperation with the base station through the useof a rate set identifier broadcast by base station on the forward link,and a RRI (reverse rate indicator) sent on the reverse link as discussedin detail above. The rate set identifies either the low rate set or thehigh rate set. Signaling is transmitted on the dedicated controlchannel.

FIG. 22 is a table of an example set of reverse traffic channel codingand modulation parameters for a low rate set (one supplemental channel),and FIG. 23 is a table of an example set of reverse traffic channelcoding and modulation parameters for a high rate set (two supplementalchannels). Parameters are shown for seven different sets of parameters,each set of parameters being distinguished by a different reverse rateindicator. Each set of parameters has a respective data rate, encoderpacket size, overall code rate, code symbols/Packet, code symbol rate,interleaved packet repeats, mod. Symbol rate, data modulation, and PNchips per encoder bit. Reverse rate indicator 0 means that there is nodedicated control or supplemental channel content. Reverse rateindicator 1 means that only the dedicated control channel is being usedon the reverse link. Rate indicators 2 through 7 relate to supplementalchannel content. In the event a user is also transmitting voice, thiswould be transmitted on the fundamental channel.

R-CHESS Channel

A channel estimate and sector selector reporting scheme for wireless airinterface is provided by an embodiment of the invention. In this scheme,by time division multiplexing channel estimate and sector selectorinformation (compared to sending the information simultaneously), thebit rate is reduced significantly and reverse link capacity is improved.A handoff mechanism is also provided which uses the sector selector andchannel estimate information.

In the new scheme, channel conditions are reported in an objectivemanner. A wireless terminal may report its channel estimate to a basestation to help the base station to determine the data transmissionrate. A wireless terminal may also monitor all the sectors it canreceive, and select the best one and report it. With the channelestimate and sector selector information, base stations can use goodchannel conditions more efficiently and improve forward link throughput.In the new reporting scheme, in every eight consecutive time slots,wireless terminals report channel estimates in the seven consecutiveslots and report sector selector information in one slot.

The new channel is referred to herein as the R-CHESS channel, standingfor Reverse CHannel Estimate and Sector Selector (R-CHESS) channel. Thestructure of the R-CHESS channel is shown in FIG. 17B. Three bits areused to represent a channel estimate or a change in channel estimate300, and three bits are used to represent sector selector symbols 302.The channel estimate or change in the channel estimate is mapped to thethree bit CHE or Δ-CHE value depending on the coding scheme of thechannel estimate. CHE represents the current channel estimate, whileΔ-CHE represents the difference between the current channel estimate andthe previous channel estimate. These are time division multiplexed 304such that seven channel estimates 300 (CHE and/or Δ-CHE) are reportedfor every one sector selection 302. The multiplexed stream is thensimplex encoded with encoder 306. The codeword is then repeated 14 timesand punctured as indicated by block 308. The result is signal pointmapped 310, and then spread by the R-CHESS channel Walsh cover 312.

The CHE (delta CHE), SS values are transmitted at a data rate of 800values per second. The timing of the CHESS channel relative to otherreverse link channels is shown in the timing diagram of FIG. 20. TheR-CHESS channel 192 is shown to have 1.25 ms slots which are one halfslot offset from the forward channels slots. In this manner, evenallowing for round trip delay, a given R-CHESS channel slot is receivedat the base station in time for the base station to use the CHEinformation for the next forward channel slot. In the illustratedexample, in a 16 slot frame, the SS is transmitted during slots 0 (SS1)and 8 (SS2), CHE is transmitted during slots 1,3,5 7,9,11,13 and 15, andΔ-CHE is transmitted during slots 2,4,6,10,12,14. In another embodiment,a CHE value is sent slots 1 to 7 and 9 to 16 and no Δ-CHE is sent.

A handoff mechanism using the R-CHESS information will now be brieflydescribed. The sector selector indicator is used to indicate the sectorthat the wireless terminal thinks it should be operating. The three bitfield can indicate one of seven sectors and a null value. As abackground process, the wireless terminal measures the pilot signalstrength of base station sectors, and when the signal strength of asector of a base station becomes sufficiently strong, this is reportedto the access network, and the sector is added to the active set for thewireless terminal. A sector select value is defined for each sector inthe active set. Similarly, when a sector's pilot strength goes below athreshold, that sector is removed from the active set.

For reverse traffic, all sectors in the active set listen totransmissions from the wireless terminal, and preferably, for eachreceive slot, the best of multiple signals received by multiple sectorsis selected as the receive signal. This provides a soft reverse linkhandoff mechanism

For forward traffic, only the sector defined by the sector select valuetransmits subject to the timing constraints below. This can change fromslot to slot. Thus, forward link handoff is completely sector selectdriven.

Preferably, for data or data/voice users, the sector select value is notallowed to change from one sector value directly to another sectorvalue. It can only change from a sector value to the null value then toa sector value.

If the sector select value changes from a sector value (for example,sector A) to the null value, the wireless terminal still reports CHEvalues for sector A for the some fixed number of slots, for example 7.Then the sector select can change to a different sector value and thewireless terminal starts to report CHE for the new sector. Forsimultaneous voice and data users, both voice and data are handed off atthe same time.

For voice only users, preferably the sector select is allowed to changedirectly from one sector value to another sector value. Also if sectorselect changes a sector value, (e.g. A to B) then the wireless terminalcontinues to report CHE for sector A for the remainder of the frame, theassumption being that voice users get one slot per frame. Then thewireless terminal begins reporting values for B.

Advanced Access Channel

A new advanced access channel described in applicant's application Ser.No. 09/983,425 published as U.S. Patent Publication No. 2002/0067701,filed Oct. 24, 2001 and hereby incorporated by reference in its entiretyimproves reverse link capacity.

An example reverse channel I and Q mapping is shown in FIG. 21A. Inputsto this are the R-CHESS channel input B, the pilot/RRI/VARQ channelinput B, DARQ channel input C, fundamental channel input D, andsupplemental channel or dedicated control channel or enhanced accesschannel or common control channel input E.

The structure of the advanced access channel shown in FIG. 21B. Theadvanced access channel or common control channel bits are added to aframe quality indicator 700, turbo encoded 702, symbol repeated insymbol repetition 704, punctured with symbol puncture 706, and thenblock interleaved with block interleaver 708. Signal point mapping isperformed 710 and then the appropriate Walsh cover applied 712.

A similar structure is employed for the fundamental channel,supplemental channel or dedicated control channel bits as indicated atFIG. 21C. The channel bits are added to a frame quality indicator 720,turbo encoded 722, symbol repeated in symbol repetition 724, puncturedwith symbol puncture 726, and then block interleaved with blockinterleaver 728. Signal point mapping is performed 730,732 and then theappropriate Walsh cover applied 734,736 with a different Walsh coverbeing applied tot he reverse supplemental or dedicated control channelthan to the reverse fundamental channel.

Numerous modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

1. A method of transmitting over a forward link in a code divisionmultiple access communications system, the method comprising:transmitting forward link frames, each frame comprising a plurality ofslots; allocating up to a predetermined maximum number of Walsh codes toa forward shared channel, scheduling a slot-wise transmission on theforward shared channel, so that each slot contains traffic for a numberof users variable from one slot to another slot, wherein in a slot forwhich said variable number of users is greater than one, the traffic fordifferent users is respectively transmitted by means of different Walshcodes allocated to the forward shared channel; and for the each slot,transmitting information identifying each user for which transmission isscheduled within said slot, over at least one user identificationchannel code-division multiplexed with the forward shared channel. 2.The method according to claim 1, wherein the Walsh codes allocated tothe forward shared channel have a Walsh length of 16 chips.
 3. A basetransceiver station for a code division multiple access communicationssystem, the transceiver station comprising: a transmitter part fortransmitting user traffic and control information over a plurality ofcode division multiplexed channels comprising a forward shared channelusing up to a predetermined maximum number of Walsh codes fortransmission of the user traffic in successive time slots and at leastone user identification channel using another Walsh code; and ascheduler for scheduling a slot-wise transmission on the forward sharedchannel so that each slot contains traffic for a number of usersvariable from one slot to another slot, wherein in a slot for which saidvariable number of users is greater than one, the traffic for differentusers is respectively transmitted over the forward shared channel bymeans of different Walsh codes, and wherein the at least one useridentification channel carries, for each slot, control informationidentifying each user for which transmission is scheduled within saidslot.
 4. The base transceiver station according to claim 3, wherein theWalsh codes used for the forward shared channel have a Walsh length of16 chips.
 5. A wireless terminal for a code division multiple accesscommunications system, the terminal comprising: a receiver part adaptedto receive user traffic over a forward shared channel, wherein theforward shared channel uses up to a predetermined maximum number ofWalsh codes for transmission of the user traffic in successive timeslots, transmission on the forward shared channel being scheduledslot-wise so that each slot contains traffic for a number of usersvariable from one slot to another slot, wherein in a slot for which saidvariable number of users is greater than one, the traffic for differentusers is respectively transmitted over the forward shared channel bymeans of different Walsh codes, and wherein the receiver part is furtheradapted to decode a user identification channel to determine if acurrent slot of the forward shared channel contains traffic for thewireless terminal, the user identification channel being code divisionmultiplexed with the forward shared channel.
 6. The wireless terminalaccording to claim 5, wherein the Walsh codes used for the forwardshared channel have a Walsh length of 16 chips.
 7. A code divisionmultiple access communications system, comprising a base transceiverstation and a plurality of wireless terminals, wherein the transceiverstation comprises: a transmitter part for transmitting user traffic andcontrol information over a plurality of code division multiplexedchannels comprising a forward shared channel using up to a predeterminedmaximum number of Walsh codes for transmission of the user traffic insuccessive time slots and at least one user identification channel usinganother Walsh code; and a scheduler for scheduling a slot-wisetransmission on the forward shared channel so that each slot containstraffic for a number of users variable from one slot to another slot,wherein in a slot for which said variable number of users is greaterthan one, the traffic for different users is respectively transmittedover the forward shared channel by means of different Walsh codes, andwherein the at least one user identification channel carries, for eachslot, control information identifying each user for which transmissionis scheduled within said slot, and wherein at least one of the wirelessterminals has a receiver part adapted to receive the user traffic overthe forward shared channel and to decode the user identification channelto determine if a current slot of the forward shared channel containstraffic for said at least one of the wireless terminal.
 8. The codedivision multiple access communications system according to claim 7,wherein the Walsh codes used for the forward shared channel have a Walshlength of 16 chips.